Projector

ABSTRACT

A projector includes an image forming unit, a projection unit, an image capturing unit, and a detection unit. The image forming unit generates projection image data based on a video signal. The projection unit projects a projection image based on the projection image data, on a projection surface. The image capturing unit generates captured image data by capturing an image of the projection surface for each line or for each block. The detection unit detects an object other than the projection image, which included in the captured image data, based on the captured image data and the projection image data. The projection unit switches projection image for each line or for each block, by scanning. The image capturing unit starts sequential image capturing from a region of the projection surface, in which switching is completed, during a period when at least switching of the projection image is performed.

BACKGROUND

1. Technical Field

The present invention relates to a projector.

2. Related Art

A technology of specifying position coordinates of a pointer such as afinger in a manner that a projection image is captured by one or aplurality of cameras and the captured image is analyzed is known. Thereis a problem in that, when the captured image is analyzed, theprojection image included in the captured image functions as noise andthus reproduction of the captured image is disturbed. Until now, atechnology of specifying a pointed position by performing differenceprocessing between the captured image and the projection image isproposed (for example, JP-A-2008-152622). In this technology, thecaptured image and the projection image are stored in a frame memory,and then timings of both the images are caused to coincide with eachother in a frame unit.

However, in the related art, there is a problem in that crosstalk inwhich images of frames before and after the projection image areincluded in the captured image occurs.

SUMMARY

An advantage of some aspects of the invention is to solve at least apart of the problems described above, and the invention can beimplemented as the following configurations.

According to an aspect of the invention, a projector is provided. Theprojector includes an image forming unit, a projection unit, an imagecapturing unit, and a detection unit. The image forming unit generatesprojection image data based on a video signal. The projection unitprojects a projection image based on the projection image data, on aprojection surface. The image capturing unit generates captured imagedata by capturing an image of the projection surface for each line orfor each block. The detection unit detects an object other than theprojection image, which is included in the captured image data, based onthe captured image data and the projection image data. The projectionunit switches the projection image for each line or for each block, byscanning. The image capturing unit starts sequential image capturingfrom a region of the projection surface, in which switching iscompleted, during a period when at least switching of the projectionimage is performed.

According to the projector of this aspect, since the image capturingunit starts sequential image capturing from a region of the projectionsurface, in which switching is completed, during a period when at leastswitching of projection image is performed, it is possible to suppressan occurrence of crosstalk of images of frames before and after theprojection image, which occurs by switching the projection image in theprocess of image capturing.

In the projector according to the aspect, the detection unit may detectthe object for each region of the projection surface and sequentiallystart the detection from a region of which image capturing is completed.According to the projector of the aspect with this configuration, sincethe detection sequentially starts from a region of which image capturingis completed, it is possible to suppress an occurrence of delay until acaptured image is processed.

According to another aspect of the invention, a projector is provided.The projector includes an image forming unit, a projection unit, animage capturing unit, and a detection unit. The image forming unitgenerates projection image data based on a video signal. The projectionunit projects a projection image based on the projection image data, ona projection surface. The image capturing unit that generates capturedimage data by capturing an image of the projection surface. Thedetection unit detects an object other than the projection image, whichis included in the captured image data, based on the captured image dataand the projection image data. The projection unit switches a projectionimage by scanning. The image capturing unit performs image capturingduring a period when switching of the projection image by the projectionunit is not performed.

According to the projector of this aspect, since the image capturingunit performs image capturing during a period when switching of theprojection image by the projection unit is not performed, it is possibleto suppress an occurrence of crosstalk of images of frames before andafter the projection image, which occurs by switching the projectionimage in the process of image capturing.

In the projector according to the aspect, the detection unit may detectan object from an image obtained by background removal processing, afterthe background removal processing of removing the projection image datafrom the captured image data is performed. According to the projector ofthe aspect with this configuration, it is possible to detect an objectfrom an image after the background removal processing.

The invention can be realized by various forms other than the projector.For example, the invention can be realized by a control method of theprojector or a form such as an interactive projection system.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanyingdrawings, wherein like numbers reference like elements.

FIG. 1 is a perspective view illustrating a projector system accordingto a first exemplary embodiment of the invention.

FIG. 2 is a block diagram illustrating a configuration of the projectorsystem.

FIG. 3 is a diagram illustrating a relationship between projection imagedata, a projection image, and a captured image.

FIG. 4 is a timing chart illustrating an operation from when a videosignal of a projector is input until background removal processing iscompleted.

FIG. 5 is an enlarged diagram illustrating a selected portion of thetiming chart.

FIG. 6 is a diagram illustrating liquid crystal driving and driving of acamera at a time point t1 illustrated in FIG. 5.

FIG. 7 is a diagram illustrating the liquid crystal driving and thedriving of the camera at a time point t2 illustrated in FIG. 5.

FIG. 8 is a diagram illustrating the liquid crystal driving and thedriving of the camera at a time point t3 illustrated in FIG. 5.

FIG. 9 is a timing chart according to a second exemplary embodiment.

DESCRIPTION OF EXEMPLARY EMBODIMENTS A. First Exemplary Embodiment

FIG. 1 is a perspective view illustrating a projector system 300according to a first exemplary embodiment of the invention. The system300 includes a projector 100 and a projection plate 200. One surface ofthe projection plate 200 is used as a projection surface SS. In theexemplary embodiment, the projector 100 is fixed to an upper portion ofthe projection plate 200 by a supporting member 910.

The projector 100 projects a projection image PS on the projectionsurface SS. Generally, the projection image PS includes an image(drawing image) drawn in the projector 100. In a case where the drawingimage is not provided in the projector 100, the projection image PS isirradiated with light from the projector 100, and thus a white image isdisplayed. In this specification, the projection surface SS means asurface of a member, on which an image is projected. The projectionimage PS means a region of an image projected on the projection surfaceSS by the projector 100. Generally, the projection image PS is projectedon a portion of the projection surface SS.

The projector 100 also captures an image of the projection surface SS.The projector 100 detects an object (for example, finger 500) other thanthe projection image PS, by comparing the captured image and theprojected image. The projector 100 is an interactive projector thatperforms an input operation by a user, based on position information ofthe detected finger 500. In this exemplary embodiment, an operation bythe finger 500 is described. For example, an operation by a pen typepointer is also possible.

FIG. 2 is a block diagram illustrating an internal configuration of theprojector 100. The projector 100 includes an image forming unit 10, aprojection unit 20, an image capturing unit 30, a captured imagecorrection unit 40, a background removal processing unit 50, a detectionunit 60, a frame memory 70, a line memory 80, and a capturing timingcontrol unit 90.

The image forming unit 10 includes a video processing unit 12 and adrawing processing unit 14. The image forming unit 10 generatesprojection image data based on the input video signal. Specifically, thevideo signal is subjected to video processing by the video processingunit 12. For example, color correction or high image quality processingmay be used as the video processing. The video signal subjected to thevideo processing is subjected to drawing processing by the drawingprocessing unit 14. The drawing processing is, for example, processingof performing an instruction (drawing, selection of a tool, or the like)of a user based on pointed position information which will be describedlater. The projection image data generated by the image forming unit 10is stored in the frame memory 70.

The frame memory 70 is a volatile memory in which a plurality of storageareas are provided. The frame memory 70 may store plural pieces ofprojection image data. In this exemplary embodiment, the frame memory 70may store three types of projection image data. The three types ofprojection image data are projection image data which will be projectednext, projection image data which is being projected at present, andprojection image data which has been projected before. The frame memory70 is connected to the projection unit 20 and the background removalprocessing unit 50 so as to cause the projection unit 20 and thebackground removal processing unit 50 to read projection image data. Theframe memory 70 may switch a storage area to be connected to each of theimage forming unit 10, the projection unit 20, and the backgroundremoval processing unit 50. The number of the storage areas of framememories 70 may be randomly changed.

The projection unit 20 projects a projection image PS onto theprojection surface SS, based on projection image data stored in theframe memory 70. The projection unit 20 includes a liquid crystaldriving unit 22, a liquid crystal panel 24, and a projection lightsource 26. The liquid crystal driving unit 22 sequentially reads piecesof projection image data stored in the frame memory 70 and drives theliquid crystal panel 24. The liquid crystal driving unit 22 drives theliquid crystal panel 24 alternately between the positive polarity andthe negative polarity, so as to suppress an occurrence of burn-in of theliquid crystal panel 24. The liquid crystal driving unit 22 controls theliquid crystal panel 24 to display the projection image PS byprogressive scanning. The liquid crystal driving unit 22 generates adriving timing signal indicating a timing for driving the liquid crystalpanel 24, and transmits the generated driving timing signal to thecapturing timing control unit 90. The projection light source 26 isrealized by, for example, a halogen lamp and a laser diode. A drawingimage drawn in the liquid crystal panel 24 based on the projection imagedata is projected onto the projection surface SS by the projection lightsource 26. Instead of the liquid crystal panel 24, other lightmodulation devices such as a digital mirror device may be used.

In this exemplary embodiment, the projection unit switches theprojection image PS by line progressive scanning. That is, depictiononto the liquid crystal panel 24 is performed for each one line, and aline at which drawing is performed is sequentially updated in a scanningdirection which is perpendicular to a line direction. Instead of lineprogressive scanning, block progressive scanning may be employed. In acase which will be described later, drawing to the liquid crystal panel24 is performed for each one block which is configured by a plurality oflines.

The capturing timing control unit 90 is connected to the liquid crystaldriving unit 22 and the image capturing unit 30. The capturing timingcontrol unit 90 generates a capturing timing signal based on the drivingtiming signal generated by the liquid crystal driving unit 22. Thegenerated capturing timing signal is transmitted from the capturingtiming control unit 90 to the image capturing unit 30.

The image capturing unit 30 captures an image of an image capturingregion MR (FIG. 3 which will be described later) including theprojection surface SS, and thus generates captured image data. The imagecapturing unit 30 is connected to the capturing timing control unit 90and the line memory 80. The image capturing unit 30 includes two cameras32 a and 32 b. A timing for image capturing by the image capturing unitis controlled based on the capturing timing signal transmitted from thecapturing timing control unit 90, and is controlled so as to cause theimage capturing unit 30 to drive with synchronization with driving ofthe projection unit 20.

As the cameras 32 a and 32 b, a rolling shutter type camera in which anexposure period is sequentially shifted for each line or for each blockin a screen is employed. The “block” means a region configured by aplurality of lines. If the image capturing region MR is divided into aplurality of regions, each of the cameras 32 a and 32 b opens a shutterfor each of the divided regions, so as to start sequential exposure.Each of the cameras 32 a and 32 b closes the shutter in a region ofwhich exposure has early started, so as to end sequential exposure. Eachof the cameras 32 a and 32 b sequentially outputs captured image datacorresponding to the region of which the exposure has been ended, to theline memory 80. In this exemplary embodiment, the cameras 32 a and 32 bare cameras which perform image capturing by receiving light in avisible region, and may be cameras using light in a region (for example,near-infrared region) other than the visible region. The number ofcameras 32 a and 32 b provided in the image capturing unit 30 is notlimited to two. For example, one camera may be provided, or three ormore cameras may be provided. In the following descriptions, in a casewhere there is no need to distinguish the two cameras 32 a and 32 b fromeach other, the cameras 32 a and 32 b are collectively referred to as “acamera 32”.

The captured image correction unit 40 is connected to a storage unit 42and the line memory 80. The storage unit 42 is a non-volatile memory.The captured image correction unit 40 takes in pieces of captured imagedata which have been sequentially output to the line memory 80 by theimage capturing unit 30. The captured image correction unit 40sequentially performs correction processing on the taken pieces ofcaptured image data. The correction processing is, for example,processing of correcting distortion of captured image data based oncalibration information stored in the storage unit 42 and of adjustingthe number of pixels of the captured image data so as to coincide withthe number of pixels of projection image data. When the correctionprocessing is performed, captured image data of the surrounding region,which is stored in the line memory 80 is also used in addition tocaptured image data to be subjected to the correction processing. Thecaptured image correction unit 40 outputs captured image data (correctedcaptured image) after the correction processing is performed, to theline memory 80. A memory which allows storing of data corresponding tolines of which the number is smaller than the number of linescorresponding to one screen of the camera 32 is used as the line memory80. For example, the number of lines for the line memory 80 may be setto be equal to or smaller than 1/10 of the number of lines for thecamera 32. The number of lines required as storage capacity of the linememory 80 is determined in accordance with a method of the correctionprocessing in the captured image correction unit 40 or detectionprocessing in the detection unit 60.

The background removal processing unit 50 is connected to the framememory 70 and the line memory 80. The background removal processing unit50 sequentially takes in corrected captured images which have beensequentially output to the line memory 80 by the captured imagecorrection unit 40. The background removal processing unit 50sequentially performs background removal processing on the correctedcaptured images which have been taken in. Specifically, the backgroundremoval processing unit 50 reads the corrected captured image and aportion of the projection image data, from the frame memory 70. Then,the background removal processing unit 50 removes the background bydifference processing between the projection image PS and the readcaptured image data. The portion of the projection image datacorresponds to data in the projection image data at positions of pixelscorresponding to the corrected captured image. In this exemplaryembodiment, as the background removal processing, the differenceprocessing performed by simple subtraction is employed, but it is notlimited thereto. The background removal processing may be a method ofremoving a background image based on a comparison between the projectionimage PS and the captured image. For example, processing of comparingimages captured by the first camera 32 a and the second camera 32 b maybe added. If the background removal processing is completed, thebackground removal processing unit 50 outputs captured image data(captured image after removal) after the background removal processing,to the line memory 80.

The detection unit 60 is connected to the line memory 80 and the drawingprocessing unit 14. The detection unit 60 detects the finger 500included in the captured image after removal, and transmits pointedposition information as a detection result, to the drawing processingunit 14. The detection unit 60 includes a finger detection unit 62 and afingertip coordinate detection unit 64.

The finger detection unit 62 detects a finger region by a templatematching method. The finger region is a region in which the finger 500is included in the captured image data. In the template matching method,the captured image after removal is compared to a template image whichhas been previously prepared. In a case where the finger 500 isdetected, the finger detection unit 62 transmits a detection result tothe fingertip coordinate detection unit 64. The finger detection unit 62detects the finger 500 in a unit of a region which is smaller than theentirety of the projection image PS. The finger detection unit 62 maysequentially take in pieces of captured image data from the line memory80 and sequentially start the detection from a region of which imagecapturing is completed.

The fingertip coordinate detection unit 64 obtains the center of gravityof the finger region, and thus calculates coordinates (fingertipcoordinates) of the tip of the finger 500 in the captured image data.The fingertip coordinate detection unit 64 calculates fingertip positioninformation which is three-dimensional coordinates which are obtained byactual pointing of the finger 500. The fingertip position information iscalculated based on the fingertip coordinates in each piece of capturedimage data of the first camera 32 a and the second camera 32 b, by usingthe principle of triangulation. The calculated fingertip positioninformation is transmitted from the fingertip coordinate detection unit64 to the drawing processing unit 14.

In a case where the driving timing signal is not correctly output fromthe liquid crystal driving unit 22, the detection unit 60 may notperform the detection processing. In a case where the driving timingsignal is not correctly output, a video is not correctly projected dueto some reasons. Thus, erroneous fingertip position information may beobtained. Thus, in this case, if the detection processing is set not tobe performed, it is possible to prevent performing of erroneous drawingprocessing using erroneous fingertip position information.

FIG. 3 is a diagram illustrating a relationship between projection imagedata PD displayed in the liquid crystal panel 24, projection image PS onthe projection surface SS, and a captured image Vc. The projector 100projects a rectangular projection image PS on the projection surface SS.Thus, the projection image PS and the projection image data PD areimages similar to each other. The captured image Vc obtained by thecamera 32 is an image obtained by capturing an image of the imagecapturing region MR. The image capturing region MR is a region whichincludes the projection surface SS and thus is wider than the projectionsurface SS. A projection image region PSR in the captured image Vc, inwhich the projection image PS is captured includes barrel distortionbased on trapezoidal distortion which is caused in an image capturingdirection, and distortion aberration of an imaging lens. In thisexemplary embodiment, only the projection image region PSR in thecaptured image Vc is cut out by the correction processing which isperformed by the captured image correction unit 40 (FIG. 2), and then isconverted into image data having the number of pixels, which is equal tothat of the projection image PS.

When the liquid crystal panel 24 displays the projection image PS, theliquid crystal panel 24 performs display by line progressive scanning.The projection image PS projected on the projection surface SS is alsoswitched in accordance with scanning of the liquid crystal panel 24. Theprojection image PS is sequentially switched from a line L1 positionedon the top side toward a line Ln positioned on the bottom side. Adirection from the line L1 toward the line Ln is referred to as aprojection scanning direction SD. When the projection image PS isswitched, a region in which an image before switching is displayed and aregion in which an image after switching is displayed are provided. Ifimage capturing is performed by the camera 32 during a period whenregions in which different images are displayed are respectivelyprovided, crosstalk may occur.

As described above, a rolling shutter type camera is employed as thecamera 32, and the camera 32 captures an image of the projection imagePS for each line or for each block. The camera 32 moves a region inwhich sequential exposure starts, in a capturing scanning direction BDindicated by an arrow. The capturing scanning direction BD is controlledto be parallel to the projection scanning direction SD of the projectionimage PS captured in the projection image region PSR. For example, whencalibration information is acquired, a positional relationship betweenthe projection unit 20 and the image capturing unit 30 may be acquired,and the capturing scanning direction BD may be calculated based on theacquired positional relationship. For example, in the dispositionillustrated in FIG. 1, both the projection scanning direction SD and thecapturing scanning direction BD are directions from an upper part of theprojection surface SS toward a lower part thereof. In a case where thedisposition in FIG. 1 is made upside down and the projector 100 performsprojection from the lower part of the projection surface SS, theprojection scanning direction SD and the capturing scanning direction BDare also inverted directions of those in a case of the disposition inFIG. 1. A line on the most upstream side of the capturing scanningdirection BD in the image capturing region MR is referred to as a lineB1. A line on the most downstream side thereof is referred to as a lineBn. A line which includes an end portion T1 of the projection imageregion PSR on an upstream side of the capturing scanning direction BDand is perpendicular to the capturing scanning direction BD is referredto as a line B(T1). A line which includes an end portion Tn of theprojection image region PSR on a downstream side of the capturingscanning direction BD and is perpendicular to the capturing scanningdirection BD is referred to as a line B(Tn).

FIG. 4 is a timing chart of an operation from when a video signal of theprojector 100 is input until the background removal processing iscompleted. V1 to V4 in FIG. 4 are pieces of image data which correspondto 4 frames and are projected as the projection image PS. V0 c to V3 care pieces of captured image data obtained by capturing images of theprojection images PS when the pieces of image data V0 to V3 areprojected, respectively. nV0 to nV3 are pieces of image data obtained byperforming the difference processing (background removal processing) onthe pieces of captured image data V0 c to V3 c, respectively. Acrosstalk time ct refers to a period when switching of the projectionimage PS is performed and to a period when crosstalk may occur.

The projector 100 operates based on a vertical synchronization signalwhich is input at a frequency of 60 Hz, for example. A video signalinput to the projector 100 and projection image data input to the liquidcrystal driving unit 22 from the frame memory 70 are switched withsynchronization with the vertical synchronization signal. For example,if the projector 100 receives a vertical synchronization signal p1, theinput video signal is switched from V1 to V2 and the projection imagedata input to the liquid crystal driving unit 22 is switched from V0 toV1.

The liquid crystal panel 24 is driven at a frequency of the quadruple ofthe vertical synchronization signal of an input video. If a video signalinput from the frame memory 70 is switched, the liquid crystal panel 24changes a drawing image to be displayed. For example, if the projectionimage data input to the liquid crystal driving unit 22 is switched fromV0 to V1, liquid crystal driving is sequentially switched from V0 to V1,from the line L1. The reason that liquid crystal driving is expressed byan arrow which descends obliquely in FIG. 4 is because that the arrowindicates that the liquid crystal panel 24 drives by line progressivescanning. In this exemplary embodiment, liquid crystal driving isperformed at a speed of the quadruple of that of the verticalsynchronization signal. The speed of the liquid crystal driving may beinteger multiple of the frequency of the vertical synchronizationsignal, and it is not limited to the quadruple. The liquid crystaldriving may be performed with switching driving polarity for each onescreen.

The camera 32 is driven based on a camera synchronization signal. If thecamera synchronization signal is switched from an L level to a H level,the camera 32 starts sequential exposure from the line B1 (FIG. 3). Ifthe camera synchronization signal is switched from the H level to the Llevel, the camera 32 sequentially closes the shutter from the line B1 onthe upper side, and ends exposure. Specifically, image capturing at theline B(T1) is started at a time point s1. A predetermined exposure timeet elapses from the time point s1. Then, if time reaches a time pointe1, the image capturing is completed. The exposure time et is set so asto allow two times of image capturing in a display time of an inputvideo corresponding to one frame. Image capturing at the line B(Tn) isstarted at a time point sn. The exposure time et elapses from the timepoint sn. Then, if the time reaches a time point en, the image capturingis completed. For the lines B1 to Bn at which exposure is completed,sequential image capturing is started after a shutter time st which is atime when exposure is not performed elapses. The shutter time st is setto be a time having a length which allows opening and closing of theshutter of the camera 32.

At the lines B(T1) to B(Tn) which include the projection image PS amongthe lines B1 to Bn, if the camera 32 ends exposure, captured image datais output to the line memory 80 for each one line. For example, capturedimage data for the line B(T1) is output at a time point e1, and capturedimage data for the line B(Tn) is output at a time point en.

If the captured image data is output to the line memory 80, projectionimage data corresponding to the captured image data is read from theframe memory 70, and the difference processing is performed. Forexample, if image data for the line B(T1) is output at the time pointe1, image data of a position in the projection image data, whichcorresponds to the line B(T1) is read from the frame memory 70, and thedifference processing is performed.

In this exemplary embodiment, the reason that two times of imagecapturing are performed in a display time of an input videocorresponding to one frame is to perform high dynamic range (HDR)imaging. For example, the exposure time et is set to have differentvalues in the first image capturing and the second image capturing, andcaptured images Vc obtained by two times of image capturing arecomposited. Thus, it is possible to obtain an image having a widedynamic range. In a case where HDR imaging is not performed, once ofimage capturing may be performed in a display time of an input videocorresponding to one frame.

FIG. 5 is a diagram illustrating an enlarged portion of the timingchart. FIGS. 6 to 8 are diagrams illustrating the liquid crystal drivingand driving of the camera 32 at time points t1, t2, and t3 illustratedin FIG. 5.

As illustrated in FIG. 5, switching of an image drawn in the liquidcrystal panel 24 from V0 to V1 is started at the time point t1. At thetime point t1, regarding lines of the line B1 to a line Bj1, exposure ofthe camera 32 for an image V0 is 100% completed. Regarding lines on alower side of the line Bj1, exposure for the image V0 is in progress.Regarding lines from the line B1 to a line Bk1, exposure for the nextimage V1 is started. The position of a line (referred to as a “currentdrawing line SL”) at which switching of an image in the liquid crystalpanel 24 is started is the position of the line L1. FIG. 6 illustrates adrawing state DS(t1) of the liquid crystal panel 24 at the time pointt1, an image capturing region MR(t1) in a case of being viewed throughthe lens of the camera 32, and a graph of exposure ratios Re(V0, t1) andRe(V1, t1) of the camera 32 for each of the lines B1 to Bn. The exposureratio Re(V0, t1) is an exposure ratio regarding the image V0, at thetime point t1. Similarly, the exposure ratio Re(V1, t1) is an exposureratio regarding the image V1, at the time point t1. In FIG. 6, in theimage capturing region MR(t1), an exposure start line ES at whichexposure by the camera 32 is started is positioned on an upstream sideof the current drawing line SL, and an exposure end line EE ispositioned on a downstream side of the current drawing line SL. Thecurrent drawing line SL is positioned in a region A1 which is a regioninterposed between the exposure end line EE and the exposure start lineES. The region A1 is a region in which exposure regarding the image V0is 100% completed. A region A2 between the exposure end line EE and theline B(Tn) at a lower end in a region including the projection imageregion PSR is a region in which exposure regarding the image V0 is inprogress.

As illustrated in FIG. 5, about the half of the image drawn in theliquid crystal panel 24 is switched from the image V0 to the image V1 atthe time point t2. At the time point t2, regarding lines of the line B1to a line Bj2, exposure of the camera 32 for an image V0 is 100%completed. Regarding lines on a lower side of the line Bj2, exposure forthe image V0 is in progress. Regarding lines from the line B1 to a lineBk2, exposure for the next image V1 is started. FIG. 7 illustrates adrawing state DS(t2) of the liquid crystal panel 24 at the time pointt2, an image capturing region MR(t2) in a case of being viewed throughthe lens of the camera 32, and a graph of exposure ratios Re(V0, t2) andRe(V1, t2) of the camera 32 for each of the lines B1 to Bn. The positionof the current drawing line SL in the liquid crystal panel 24 is aposition in the vicinity of the center of the liquid crystal panel 24.In FIG. 7, hatching is applied to a region in which the image V1 isdisplayed. In FIG. 7, in the image capturing region MR(t2), an exposurestart line ES at which exposure by the camera 32 is started ispositioned on an upstream side of the current drawing line SL, and anexposure end line EE is positioned on a downstream side of the currentdrawing line SL. The current drawing line SL is positioned in a regionA1 which is a region interposed between the exposure end line EE and theexposure start line ES. Thus, the current drawing line SL of the imageV1 is positioned at a position at which image capturing for the image V0is ended. Exposure for the image V0 is in the process, in a region A2 onthe downstream side of the current drawing line SL. Exposure for thenext image V1 is started, in a region A3 on the upstream side of thecurrent drawing line SL.

In the crosstalk time ct illustrated in FIG. 5, the current drawing lineSL moves with tracking a position (exposure end line EE) at whichexposures is completed, and a position (exposure start line ES) at whichexposure starts moves with tracking the current drawing line SL. Thatis, the projection image PS is sequentially switched from a region ofwhich exposure is ended and image capturing is completed, and sequentialexposure is started from a region in which switching of the projectionimage PS is completed.

As illustrated in FIG. 5, the image drawn in the liquid crystal panel 24is totally switched to the image V1 at a time point t3. At the timepoint t3, regarding lines from a line Bj3 to a line Bk3, exposure forthe image V1 is in progress. FIG. 8 illustrates a drawing state DS(t3)of the liquid crystal panel 24 at the time point t3, an image capturingregion MR(t3) in a case of being viewed through the lens of the camera32, and a graph of the exposure ratio Re(V1, t3) of the camera 32 foreach of the lines B1 to Bn. The position of the current drawing line SLin the liquid crystal panel 24 is in the vicinity of the center of theliquid crystal panel 24. In the image capturing region MR(t3), exposurefor the image V1 is in the process, in the region A3 between the lineB(T1) and the line B(Tn). The current drawing line SL is positioned inthe region A3, and the image of which exposure is in the process isswitched. However, since the entirety of the liquid crystal panel 24 isalready and completely switched to the image V1, the projection imageregion PSR is not changed. Accordingly, crosstalk does not occur.

As described above, regarding each of the lines B(T1) to B(Tn) at whichthe projection image PS is captured, only single image is displayedduring a period when exposure is performed.

According to the above-described first exemplary embodiment, the imagecapturing unit 30 starts sequential image capturing from a region of theprojection surface SS, in which switching is completed, during thecrosstalk time ct which is a period when at least switching of theprojection image PS is performed. Thus, the image capturing unit 30 iscontrolled not to switch a projection image PS which is in the processof being captured, and can suppress the occurrence of crosstalk byimages of frames before and after the corresponding image. Accordingly,in the projector 100, it is possible to reduce noise in the capturedimage Vc and to compare the projection image PS and the captured imageVc to each other with high grade.

In the first exemplary embodiment, sequential detection is started froma region of which image capturing is completed. Thus, it is possible tosuppress the occurrence of delay until the captured image is processed.As a result, it is easy to detect a pointed position in real time.

In this exemplary embodiment, image capturing can also be performed in aperiod between crosstalk times ct. Thus, it is possible to increase theexposure time et in comparison to that in a case where image capturingis not performed in a period between the crosstalk times ct.

Since the projector 100 performs two times of image capturing during aperiod of one frame, it is possible to acquire two captured images Vcfor the same projection image PS. In this case, it is possible toperform HDR imaging by using the two captured images Vc. Accordingly, itis possible to extend the gradation of the captured image Vc incomparison with that in a case where one captured image for oneprojection image PS is acquired.

Driving of the image capturing unit 30 is controlled by the capturingtiming signal based on the driving timing signal generated by the liquidcrystal driving unit 22. Therefore, in a case where the projection unit20 does not normally operate, the driving of the image capturing unit 30is suspended. Accordingly, it is possible to suppress erroneousoperation when the projection image PS is not displayed.

B. Second Exemplary Embodiment

A projector 100 according to a second exemplary embodiment is differentfrom the first exemplary embodiment in that the camera 32 provided inthe image capturing unit 30 is a global shutter type. In the globalshutter type camera, image capturing (exposure) for the entirety of theimage capturing region simultaneously starts, and image capturing issimultaneously ended. Other components are similar to those in the firstexemplary embodiment.

FIG. 9 is a timing chart in the second exemplary embodiment. Theprojector 100 does not perform image capturing during a period betweencrosstalk times ct. The projector 100 performs once of image capturingduring a period when images corresponding to one frame are drawn 4times. The projector 100 starts image capturing after the crosstalk timect is finished, and ends the image capturing before the next crosstalktime ct starts. Since other kinds of driving are similar to those in thefirst exemplary embodiment, descriptions thereof will not be repeated.

The above-described projector 100 according to the second exemplaryembodiment performs image capturing during a period when switching of aprojection image PS by the projection unit 20 is not performed, that is,a period other than the crosstalk time ct. Thus, it is possible tosuppress an occurrence of a situation in which the projection image PSwhich is in the process of being captured is switched, and thuscrosstalk occurs by images of frames before and after the correspondingimage. Accordingly, in the projector 100, it is possible to reduce noisein the captured image Vc and to compare the projection image PS and thecaptured image Vc to each other with high grade. As in the firstexemplary embodiment, even in a case where the camera 32 of a rollingshutter type is used, image capturing may be performed during a periodother than the crosstalk time ct.

The invention is not limited to the above-described exemplaryembodiments, and can be realized with various configurations in a rangewithout departing from the gist of the invention. For example, technicalfeatures in the example corresponding to the technical features in theaspects described in the section of the summary can be suitably replacedor combined in order to solve some or all of the above-describedproblems or to achieve some or all of the above-described effects. Thetechnical features can be suitably deleted so long as it is notdescribed that the technical features are necessary.

The entire disclosure of Japanese Patent Application No. 2017-059315,filed Mar. 24, 2017 is expressly incorporated by reference herein.

What is claimed is:
 1. A method for controlling a projector comprising: generating projection image data based on a video signal; projecting a projection image based on the projection image data, on a projection surface by a projection unit; generating captured image data by capturing an image of the projection surface for each line or for each block by an image capturing unit; and detecting an object other than the projection image, which is included in the captured image data, based on the captured image data and the projection image data, wherein the projection unit switches the projection image for each line or for each block, by scanning, and the image capturing unit starts sequential image capturing from a region of the projection surface, in which switching is completed, during a period when at least switching of the projection image is performed.
 2. The method for controlling the projector according to claim 1, further comprising: detecting the object for each region of the projection surface sequentially from a region of which image capturing is completed.
 3. A method for controlling a projector comprising: generating projection image data based on a video signal; projecting a projection image based on the projection image data by a plurality of scanning in a frame, on a projection surface by a projection unit; generating captured image data by capturing an image of the projection surface by an image capturing unit; and detecting an object other than the projection image, which is included in the captured image data, based on the captured image data and the projection image data, wherein the projection unit switches the projection image by first scanning in the frame, and the image capturing unit performs image capturing during a period from second scanning to last scanning in the frame by the projection unit.
 4. The method for controlling the projector according to claim 1, further comprising: detecting the object from an image obtained by background removal processing, after the background removal processing of removing the projection image data from the captured image data is performed. 